Catalyst component-loaded honeycomb structures have been used in exhaust gas purification devices for heat engine (e.g. internal combustion engine) or burner (e.g. boiler), reformers of liquid fuel or gaseous fuel, etc. Also, it is known to use a honeycomb structure as a filter for capture and removal of the particles contained in a particle-containing fluid such as exhaust gas discharged from diesel engine.
In such honeycomb structures used for the above purpose, non-uniform temperature distribution tends to appear inside owing to the sudden temperature change of exhaust gas or the local heat generation, which has caused problems such as cracking. In order to alleviate these problems, it was proposed to constitute a honeycomb structure in an integral structure of a plurality of honeycomb segments, by bonding individual honeycomb segments with an elastic bonding material, to relax the thermal stress applied to the structure.
Further, in mounting a diesel particulate filter (a DPF) of honeycomb structure beneath the floor of vehicle, a DPF of large size is used in order to deposit a larger amount of particles for improvement of fuel consumption, or there is used, in some cases, a DPF in which the opening ratio of inlet cells is higher than the opening ratio of outlet cells, for lower pressure loss.
However, there were cases that the deposition of a larger amount of particles caused cracks at the downstream end face of DPF owing to the thermal stress appearing when the deposited particles were burnt for regeneration.
In Patent Document 1 it is disclosed a technique of using a higher plugging ratio at the center of end face of honeycomb structure than at the periphery of end face of honeycomb structure to suppress the temperature elevation during the regeneration of honeycomb structure and enhance the limit of crack generation.
In Patent Document 2 it is disclosed a technique of deepening the plugged portion at the center of end face of honeycomb structure to suppress the temperature elevation during the regeneration of honeycomb structure.
Patent Document 1: WO 2005/014142
Patent Document 2: JP-A-2004-162537